For years, social scientists have tried to explain why living together before marriage seemed to increase the likelihood of a couple divorcing. Now, new research released by the nonpartisan Council on Contemporary Families gives an answer:

It doesn't. And it probably never has.

This is despite two decades of warnings from academics and social commentators who pointed to studies that claimed a correlation between "shacking up" and splitting up—warnings that increased as the number of couples living together before marriage skyrocketed.

As it turns out, those studies that linked premarital cohabitation and divorce were measuring the wrong variable, says Arielle Kuperburg, a professor at the University of North Carolina, Greensboro, who produced much of the research released Monday. The biggest predictor of divorce, she says, is actually the age at which a couple begins living together, whether before the wedding vows or after.